Nitisinone is a drug originally developed as an herbicide

Herbicide

Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

 now used in the treatment of hereditary tyrosinemia type 1. Since its first use for this indication in 1991, it has replaced liver transplantation

Liver transplantation

Liver transplantation or hepatic transplantation is the replacement of a diseased liver with a healthy liver allograft. The most commonly used technique is orthotopic transplantation, in which the native liver is removed and replaced by the donor organ in the same anatomic location as the original...

 as the first-line treatment for this rare condition. It is also being studied in the less severe but related condition alkaptonuria

Alkaptonuria

Alkaptonuria is a rare inherited genetic disorder of phenylalanine and tyrosine metabolism. This is an autosomal recessive condition that is due to a defect in the enzyme homogentisate 1,2-dioxygenase , which participates in the degradation of tyrosine...

. It is marketed under the brand name Orfadin.

The mechanism of action

Mechanism of action

In pharmacology, the term mechanism of action refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect...

 of nitrisinone involves reversibile inhibition

Enzyme inhibitor

An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...

 of 4-hydroxyphenylpyruvate oxidase

4-hydroxyphenylpyruvate oxidase

In enzymology, a 4-hydroxyphenylpyruvate oxidase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are 4-hydroxyphenylpyruvate and O2, whereas its two products are 4-hydroxyphenylacetate and CO2....

, thus preventing the formation of maleylacetoacetic acid and fumarylacetoacetic acid, which have the potential to be converted to succinyl acetone, a toxin that damages the liver and kidneys.